One form of the invention relates to a printing control device incorporated in an image processing device for displaying an observed image on a display screen. One form of the invention relates to an image processing device for displaying an observed image on a display screen. One form of the invention relates to a printing control method performed in an image processing device for displaying an observed image on a display screen. One form of the invention relates to a program executed by a computer included in an image processing device for displaying an observed image on a display screen.
One form of the invention relates to a printing control device included in a printing device. One form of the invention relates to a printing device. One form of the invention relates to a printing control method performed by a printing device. One form of the invention relates to a program executed by a computer included in a printing device.
The conversion of medical information into electronic information has now been under way in medical fields. Accordingly, an environment is being put in order in which an image for medical diagnosis which image is photographed by an electronic photographing device can be observed immediately after photographing.
Images for medical diagnosis include for example X-ray photographed images, MR images, and others. As referred to as “see-through shadows,” most of images of this kind are single-color images. In addition, images of this kind do not have stereoscopic shading for providing perceived depth to a subject. Therefore, light and shade represented as a shadow is the only information of images of this kind.
Hence, reproducibility of light and shade information on a display screen or printed matter is important to images for medical diagnosis. That is, reproducibility of gradation of an image is essential for quick diagnosis and accurate diagnosis.
There are cases where the brightness and contrast of an observed image are desired to be changed to observe an affected part or another area of interest displayed on a display device in more detail.
In addition, because a manner in which an observed image is seen on a display screen differs depending on an environment where the display device is installed, for example the brightness of a room or the like, there are cases where the brightness and contrast of the image are desired to be changed for easier observation.
From such necessity, application software has been developed which provides a plurality of gamma characteristics selectable by an observer and thereby enables gradation of the observed image to be changed. Description thereof will be made in more detail.
FIG. 1 shows an example of a typical image printing system. This image printing system includes: an image processing device 1 for processing an observed image; a display device 3 for displaying the observed image; and a printing device 9 for printing image data (printing data) supplied via a communication path 5 or an external storage medium 7.
The communication path 5 may be a wire path or a wireless path, and may be formed via a network. A portable storage medium, for example a semiconductor memory, an optical storage medium, a magnetic storage medium or the like is used as the external storage medium 7.
FIG. 2 shows an example of display of a monochrome image by application software started by the image processing device 1. This application software has a function that enables an observer to change characteristics of gradation reproducibility of an image display system through a user interface. FIG. 3 shows an example of the user interface. In this example, five gamma buttons are provided to allow selection or adjustment of a gradation correction curve.
FIG. 4 shows an example of gradation correction curves (hereinafter referred to also as “gamma correction curves”). The brightness of image display can be changed by correcting original image data by these curves.
In this example, M-Curve (a) produces a darkest image, and M-Curves (b), (c), and (d) produce brighter images in that order. M-Curves (a) to (d) correspond to curves A to D in FIG. 3.
Incidentally, when a custom input is selected on the user interface, an arbitrary curve can be selected by a drag-and-drop operation of a mouse. FIG. 5 shows an example of a gradation correction curve based on a cubic curve function and an example of the user interface.
In general, a display device including a display device of a CRT (Cathode Ray Tube) system does not have a linear proportional relation as a brightness characteristic of an output value with respect to an input value, and has a curved output characteristic specific to the display device, in which the display device starts emitting light gradually at a certain value and then sharply increases a light quantity. This curve is referred to as the “gamma curve of the monitor”.
Hence, when image data is supplied to the display device as it is without gradation correction, gradation distortion of a displayed image is inevitable. In practice, however, image data handled by a computer is initially created according to the curve, so that there is no fear of distortion in reproduction characteristics.
FIG. 6 shows a typical gamma curve of a CRT. A curve represented by alternate long and short dashed lines in the figure is an input-output characteristic used as a de facto standard in a computer display. Hence, when a gamma curve specific to a display differs from the de facto standard gamma curve, reproduction characteristics thereof may be adjusted to the de facto standard gamma curve within the computer to maintain compatibility of images and graphic data.
When an image having an opposite tendency from that of this gamma curve is created, characteristics of reproduction of gradation by a brightness output of the CRT can be kept substantially linear in a dark-to-bright range. The tendency of the image data is represented by a broken line in FIG. 6. Gamma-corrected reproduction characteristics are represented by a solid line in FIG. 6.
However, the linearity of the gradation created according to this gamma curve is limited to a case where ambient brightness satisfies a certain precondition.
Hence, when surroundings of the CRT are extremely bright, an observed image is observed as a very dark image, whereas when surroundings of the CRT are extremely dark, an observed image is observed as a very bright image.
Thus, the gradation of an observed image is not maintained in a best state at all times. In fact, depending on an environment in which the display device is installed, a better result may be obtained when there is a difference from the de facto standard gamma correction curve.
Thus, general image display systems do not have an optimum and universal gamma value.
Further, there is another reason for changing the brightness and contrast of the display device displaying an observed image. For example, the brightness and the contrast are changed for easier observation of an affected part or a specific area suspected to be an affected part.
Accordingly, when the brightness and the contrast are changed, characteristics of reproduction of gradation of an observed image need to be changed adaptively.
The above-described application software (FIG. 3) is used to change the gradation reproduction characteristics.
FIG. 7 shows an example of internal configuration of an image printing system (FIG. 1) having a function of changing the gradation reproduction characteristics by the application software.
The image processing device 1 includes an image memory 11, a variable gamma correction unit 13, a fixed gamma correction unit 15, and a printer driver 17.
The variable gamma correction unit 13 corresponds to a brightness correction process by the application software. For example, the variable gamma correction unit 13 performs a correction process using a gamma correction curve selected via the user interface screen shown in FIG. 3. The brightness correction in the variable gamma correction unit 13 is variable.
The fixed gamma correction unit 15 corresponds to a de facto standard gamma correction process. This process is a fixed process for maintaining a characteristic of reproduction of density of the display device at a certain value.
FIG. 8 shows equivalent gamma curves of the system as a whole. As a result of brightness correction made by the gamma curves by the application software, the gradation reproduction characteristics are converted nonlinearly.
[Patent Document 1]
Japanese Patent Laid-Open No. Sho 56-107674
[Patent Document 2]
Japanese Patent Laid-Open No. 2003-259122
[Patent Document 3]
Japanese Patent Laid-Open No. 2004-216559